Challenged by public opinion, peers and the Congressional Budget Office, a number of specialty societies have recently begun to develop Top Five lists of relatively expensive procedures that do not provide meaningful benefit to at least some categories of patients for whom they are commonly ordered. The Choosing Wisely(R) campaign, developed by the American Board of Internal Medicine and embraced by most of the major medical specialty societies, is the most visible example. The extent to which the development of these lists has influenced the behavior of physicians or patients, however, remains unknown. In this application, we will use the Wisconsin Collaborative for Healthcare Quality (WCHQ), a statewide consortium of hospitals, medical practices, and health systems, as a laboratory in which to examine the effectiveness of two organizational interventions: (i) a basic public reporting intervention which summarizes on a public website practice-level statistics regarding use of targeted ineffective or unproven interventions for breast cancer and (ii) an enhanced intervention, augmenting public reporting with a smart phone-based application (App) that gives providers just-in-time information, decision-making tools, and personalized patient education materials that support reductions in the use of breast cancer interventions targeted based upon Choosing Wisely(R) or national oncology society guidelines. Specifically, our aims are: (1) To examine whether basic public reporting reduces use of targeted breast cancer practices among a contemporary cohort of patients with incident breast cancer in the intervention state relative to usual care in comparison states, using Marketscan and Medicare claims data while adjusting for possible confounders and temporal trends. (2) To examine the effectiveness of the enhanced intervention relative to the basic intervention using a cluster-randomized design applied to WCHQ providers; and (3) To simulate cost savings forthcoming from nationwide implementation of both interventions (relative to each other and to usual care) and to describe the implications of these findings for reimbursement policy and program initiatives. The results will provide rigorous evidence regarding the effectiveness of a unique all-payer, all-age public reporting system that is potentially exportable to other states, a well as rigorous evidence regarding a novel method (App) for influencing provider behavior. The results will be important for all interested in the challenges of reducing ineffective or unproven care, including government, policy-makers, payers, health care providers, and consumers. The results will be further relevant to the ACO environment, which is expected to provide financial disincentives for providing ineffective or unproven care.